This tutorial assumes you have an anonabox pro with firmware version 4.3 or newer. This info is based on the official tor user documentation found here: https://www.torproject.org/docs/tor-manual.html.en
It is simple to setup your Anonabox Pro to be an exit node and share your bandwidth on the tor network. First, log in to the admin interface. Then click on the services dropdown at the top of the page, from the list of links that comes up, select tor. On that page, click the 'advanced' tab.
On the page that comes up, you are able to manually edit the torrc (tor configuration file). It is plain text. Scroll down to the bottom of that file and paste the following:
Exitpolicy reject *:*
Here is an example screenshot of how it will look:
Note that ORPort is the number of the port that you will have the device listening for incoming connection from, this port will need to be reachable from the outside world. 443 is a common one. If you have an upstream router or firewall, you will need to forward this port to the anonabox.
Nickname must be something unique using only letters and numbers and be less than 19 characters. Contact info is an email address where you can be reached if there is something wrong with your conenction. If you run a good exit node, you might be contacted at this email by the official tor proect to find out where they can mail your free t-shirt. More info can be found here:
These are great shirts btw, we have a few here at the anonabox offices.
Scroll down to the bottom of the page and click 'save and apply'. You will be redirected back to the tor status page. On that page you will want to stop and restart tor, so click the button that says 'stop' and then after the process has stopped, click on 'start tor' this will start tor and load the new configuration changes you made in the previous step.
Reasons you would want to do this can be found here: Some great tips for the ins and outs can be found at this link: